Azeotropic composition



United States Patent 3,539,462 AZEOTROPIC COMPOSITION J. Allan Schofield, Irvington, N.Y., assignor to Union Carbide Corporation, New York, N.Y., a corporation of New York No Drawing. Continuation-impart of application Ser. No. 661,847, Aug. 21, 1967. This application Oct. 17, 1968, Ser. No. 768,522

Int. Cl. C09d 9/00; (111d 7/50; C23g /02 US. Cl. 252-170 2 Claims ABSTRACT OF THE DISCLOSURE The disclosure relates to azeotropic mixtures of trichlorotrifluoroethane dichloroethane and isopropanol.

This application is a continuation-in-part of US. Pat. Application Ser. No. 661,847, filed Aug. 21, 1967 and now abandoned.

This invention relates to an azeotropic composition and particularly to the azeotropic mixture of trichlorotrifluoroethane; dichloroethane and methanol or ethanol or isopropanol or tertiary butanol or 2,2-dimethyl butane or 2,3-dimethyl butane.

Chlorofluoroethane solvents known in the art ordinarily do not have sufficient solvent power to clean printed circuit boards; that is, to effectively remove the rosin flux and other contaminants deposited on the surface of such boards during the application of conductive metal leads thereto. Ultrasonic or vapor degreasing techniques may be used to improve the cleaning action of such solvents. Although mixtures of solvents have been used for this purpose they have the disadvantage that they boil over a range of temperatures and consequently undergo fractionation in vapor degreasing or ultrasonic applications which are open to the atmosphere. Additionally, when employing either of these methods the solvent must also be relatively nontoxic and nonfiammable for safety reasons.

For certain solvent purposes some chlorofluoroethanes by themselves have insuflicient solvent power. For example, in cleaning printed circuit boards trichlorotrifiuoroethane does not have suflicient cleaning or solvency power to remove the flux, such as rosin which is employed in deposit ing metal conductors to the circuit board. Other solvents such as dichloroethane is too strong a solvent and tends to cause the circuit board to warp, swell or distort, which could in some instances lead to breaking of the conductor(s) on the board. Although mixtures of solvents may be used for cleaning circuit boards they surfer the disadvantage that they boil over a range of temperatures and consequently undergo fractionation in vapor degreasing or ultrasonic applications which are open to the atmosphere. When employing either of these methods the sol vents must also be substantially non-toxic for safety reasons.

It is an object of this invention to provide a constant boiling or azeotropic solvent that is a liquid at room temperature, will not fractionate and also has the foregoing advantages. Another object is to provide an azeotropic composition which is valuable as a solvent for oils and greases particularly for cleaning printed circuits. A further object is to provide an azeotropic composition which is both relatively nontoxic both in the liquid phase and in the vapor phase and which at the same time is an excellent solvent for cleaning printed circuits especially by continuous degreasing or ultrasonic means.

The above object of this invention may be accomplished by novel mixtures comprising a three component composition of trichlorotrifluoroethane (e.g. l,1,2-trichloro-1,2,2-

3,539,462 Patented Nov. 10, 1970 trifiuoroethane) as a first component, 1,1-dichloroethane as a second component and either methanol or ethanol or isopropanol or tertiary butanol or 2,2-dimethyl butane or 2,3- dimethyl butane as a third component. Although 1,1,2- trichloro-l,2,2-trifiuoroethane is a preferred trichlorotrifluoroethane component, the isomer 1,l,1-trichloro-2,2,2- trifiuoroethane may be substituted as a component therefore in whole or in part and especially in minor amounts or trace amounts. All of these mixtures form azeotropes which distill at a constant temperature, the liquid phase and the vapor phase in equilibrium therewith having the same composition. Such mixtures are relatively nontoxic in both the liquid phase and the vapor phase. These mixtures are particularly useful as solvents for greases, oils, waxes and the like and are particularly useful for cleaning printed circuits. 1

Although the azeotropic mixtures are obtained at approximately 160 mm. Hg a variation in pressure and consequentialy a change in the compositions and boiling points are also intended to be within the broad scope of the invention. Thus the azeotropes may contain many different proportions of the aforementioned components provided a constant boiling mixture is obtained at the various pres sures at which the compositions are used. Stated otherwise any pressure may may be employed to obtain the azeotropes of this invention as long as a three component constant boiling mixture is obtained, and accordingly the ratio of components of the azeotropes of the invention will also vary. The variation of components is thus within the skill of the art and is easily determined once it is known that the mixture of components of this invention will form the aforementioned azeotropes. In a preferred embodiment the present invention relates to the aforementioned azeotropes that boil at atmospheric pressure i about 25, especially i about 15 mm. Hg.

Azeotropic mixtures were obtained in the course of distillation of a mixture of 1,1,2-trichloro-1,2,2-trifluoroethane; 1,1-dichloroethane and methanol or ethanol or isopropanol or tertiary butanol or 2,2-dimethyl butane or 2,3-dimethyl butane. The mixtures are charged to a laboratory distillation fiask provided with an overhead condenser for the removal of ,distillate. The mixtures are heated to its atmospheric boiling point and distilled at high reflux. The azeotropic mixture is removed consisting essentially of the following compositions as determined by vapor phase chromatography the boiling points of which are measured at substantially 760 millimeter Hg pressure:

TABLE I Boiling Composition, point, percent by F.-760 Examples Components Weight mm. Hg

1,1 ,Z-trichloro-l,2,2-tri-- 1 fluoroethane 90.1 102 7 1 1 dichloroethane 4.2

2.9 1,1,t2fitrichl0ro-L2 4 8 e 8 4 L 0 115. 6

ta o1 14.2 1,1,?Ftrichlor01,2,Ztrifiuoro- 5 ethane 65.6 114 3 1,1-dichloroethane... 15. 5

2,2-dimcthyl butane 18. 9 1,1,2trichloro1,2,2-tr 6 fiuoroethane 78.9 115 8 1,1-dichloroethane. 15.2

2,3-dimethyl butane. 6. 9

Although the azeotropes are obtained at approximately remains after treatment. On the other hand, if the board is 760 IIIIIL Hg 3 Variation in Pressure and consequently a cleaned with 1,1-dichloroethane alone, even though the Change in the compositions and boiling, Points are also rosin flux is substantially removed, the board itself may intended to be within the broad scope of the invention. be considerably damaged However, if the board is treated Thus the azeotropes may contain many Proportions of an with the azeotropic compositions of this invention subthree of the components of the foregoing examp 165 stantially all of the rosin flux is removed Without any vided a constant boiling mixture is obtained at the various pressures at which the compositions are used. Stated otherwise any pressure may be employed to obtain the azeomg of the PTlIlted elfelllt- Y tropes of this invention as long as a three component con- The aZeOtTOPeS of the Present lhvehhoh are Unexpected TABLE III.-TERNARY MIXTURES THAT DO NOT FORM AZEOTROPES detrimental effect on the board which constitutes the back- 1) Solvent 113 Methylene chloride Ohlorotorm.

do. .do Carbon tetrachloride; do. .do. Isopropanol. .doJ. do. Methyl acetate.

do. -dO Acetone. 1 -dichloroethane Methyl acetate.

d d Sec-butanol. -dOJ. -do- Cyclopentane.

do .do do. 1,2-dichloroethane. Methanol do. -d0-...- Ethanol 1 1,1,2-trichloro-1,2,2-trifluoroethane.

stant boiling mixture is obtained, and accordingly the especially in view of the fact that the following ternary ratio of components of the azeotropes of the invention and binary mixtures were not found to formazeotropes:

will also vary. The variation of components is thus within TABLE ARY MIXTURES THAT o NOT FORM the skill of the art and is easily determined once it is AZEOTROPES known that the halogenated hydrocarbons of the exam- Benzene, ples will form azeotropes with methanol or ethanol or ggg gg isopropanol or tertiary butanol or 2,2-dimethy1 butane or r n l: 2,3-dimethyl butane. In a preferred embodiment, the present invention relates to the azeotropic components of l,2-dichloroethane: i about 5 and especially i about 15 mm. Hg. Although l,1,2-trichloro-1,2,2-trifluoroethane is employed as a pre- H 2:3-dimethyl butane. fer-red compound the isomer 1,1,1-trichloro-2,2,2-trifluo- S 1 nt113! ggg ggg roethane may be substituted therefore in whole or in part methane. especially in minor amounts. gg gif Because of this variation in boiling temperature due to Hexane. a change in pressure the mixtures of the present invention figgfiggg gm may vary in composition especially the azeotropic mix- Methyl ethyl ketone. tures. Accordingly, the compositions of the present invention comprises mixtures of trichlorotrifluoroethane (e.g. 1,1,1-trichloroethane. 1,1,2-trichloro 1,2,2 trifiuoroethane and 1,1 dichloro- 1 1 1 Hricmowl 2 ltrifluomethane ethane) and the other components of this invention as r follows; v 40 Although the invention has been described by reference TABLE II Components Composition, weight basis (1).. 1,1,2-t1'ichlor0-1,2,2trifiuoroethane About 90.1:babout 10%, especiallyiabout 5%. 1,1-dichloroethane. About 4.2:babout 10%, espec allyzlzabout 5%. Methanol About 5.7;];about 10%, especiallyiabout 5%.

About 86.4=!:about 10%, especiallyiabout 5%. About 8.6;];about 10%, especi allyzlzabout 5%. About 5.1iabout 10%, especiallydzabout 5%.

About 85.7iabout 10%, especialiyiabout 5%. About llAzbabout 10%, especrallyiabout 5%.

(3) 1,1,2-trichlor0-1,2,2-trifluoroethane 1,1-dichloroethane Is0pr0panol...-. About 2.9;];about 10%, especiallyiabout 5%.

(4).. 1,1,2-trichl0ro-1,2,2 triflu0r0ethane About 84.8:babout 10%, especiallyiabout 5%. 1,1-diehloroethane. About 1.0;};ab0ut 10%, espec allyzbabout 5%. Tart-butanol About 14.2=t:about 10%, especiallyiabout 5%.

About 65.6;habout 10%, especiallyiabout 5%. About 15.5:babout 10%, especiallyiabout 5%. About 18.9;babout 10%, especiallyzbabout 5%.

(5).. 1,1,2-trichloro-1,2,2-trifiu0roethane 1,1-dichlor0ethane. 2,2-dimethyl butan Although the foregoing Table II refers to 1,1,2-trito some preferred embodiments it is not intended that the chloro-1,2,2-trifluoroethane, it is also applicable to trih Scope Ofthe hovel e p e eofl'lposltlonebe chlorotrifluoroethanes as described previously herein. lted thereby but certam Fnodlficatlons are Intended A printed circuit board coated with a rosin flux is to be included w1th1n the spirit and broad scope of the 1 d 1t d t h th following claims. C Came In an n rasomc egreasmg appara us e 7 These claims cover the novel embodiments of the presmixtures of this invention and substantially all of the rosin em invention especially the Substantially nomtoxic fllvfv 1S IemOYed Wlthout Y observable effect tures noted in each. It is also intended that they cover the Whleh COIlStltuteS e haeklng Ohthe Pflhted elfehltsubstantially non-flammable mixtures of Examples 1-4 W the board 15 Cleaned Wlth LL -L Q- and 6 as well as the broad composition limits-which apply trifluoroethane alone a considerable amount of rosin fiux to these substantially non-flammable compositions. In the 81.09 parts of such halo carbon on a Weight basis and 5 likewise for the other components given in Table II and noted in the claims as well as their equivalents especially those equivalents noted herein.

What is claimed is:

1. An azeotropic composition consisting essentially of about 85.7 parts by weight of 1,1,2-trichloro-1,2,2-trifiuoroethane, about 11.4 parts by Weight of 1,l-dichlor0- ethane and about 2.9 parts by weight of isopropanol.

2. A method for cleaning a solid surface comprising contacting said surface with the composition of claim 1.

References Cited UNITED STATES PATENTS 9/1961 Bennett et al 252--170 OTHER REFERENCES Mellan: Industrial Solvents, 2nd ed. (1950) Reinhold Publ. Co., pp.7375.

Rose: Cond. Chem. Dict., 6th ed. (1961) Reinhold Publ. Co., p. 472.

US. Cl. X.R. 

